Stability Of Nanoassemblies Research Articles

Impact of the nature of the linker on the 2D and 3D organization of lipid-phenalenone conjugates

A series of phenalenone-lipid conjugates (1A, 1B, 1C, 2) have been synthesized to compensate for the poor water solubility of the photosensitizer phenalenone (PN) and promote the formation of nano-assemblies. We show that the organization and structure of monolayers upon compression strongly depend on the nature of the linker connecting PN to the lipid backbone, and the number of C18 chains. Monolayer properties at the air-water interface were analyzed by surface pressure measurements, Brewster angle and atomic force microscopies, grazing incidence X-ray diffraction, and X-ray reflectivity. Whereas conjugate 1C (ester bond) organizes into multilayers upon compression, conjugates 1A, 1B, and 2 form stable monolayers whose structure is controlled by van der Waals (vdW) interactions between C18 chains, intermolecular H-bonding involving the linker, and for 1B, π-π stacking of PN moieties. Conjugate 1A (amide-triazole linker) is structured into a rectangular network of chains with an order that extends only to the molecule of the adjacent cell. Conjugate 1B (amide bond) forms two incommensurate networks, one for the chains and the other for the headgroups. The distance between molecules in the next near neighbor chain lattice and the sufficient degree of freedom of PN groups allow the latter to pile up via π-π interactions below the chains in a rectangular cell. Conjugate 2 with its double chain adopts a similar behavior to that of a saturated phospholipid. Strong vdW interactions predominate and allow, at high surface pressure, hexagonal packing with no chain tilt. The distance between molecules prevents PN stacking. The identified PN derivative structures explain the linker’s impact on the formation and stability of nano-assemblies.

Probing the Impact of Surface Functionalization Module on the Performance of Mitoxantrone Prodrug Nanoassemblies: Improving the Effectiveness and Safety.

Prodrug nanoassemblies are emerging as a novel drug delivery system for chemotherapy, comprising four fundamental modules: a drug module, a modification module, a response module, and a surface functionalization module. Among these modules, surface functionalization is an essential process to enhance the biocompatibility and stability of the nanoassemblies. Here, we selected mitoxantrone (MTO) as the drug module and DSPE-PEG2K as surface functionalization module to develop MTO prodrug nanoassemblies. We systematically evaluated the effect of surface functionalization module ratios (10%, 20%, 40%, and 60% of prodrug, WDSPE-mPEG2000/Wprodrug) on the prodrug nanoassemblies. The results indicated that 40% NPs significantly improved the self-assembly stability and cellular uptake of prodrug nanoassemblies. Compared with MTO solution, 40% NPs showed better tumor specificity and pharmacokinetics, resulting in potent antitumor activity with a good safety profile. These findings highlighted the pivotal role of the surface functionalization module in regulating the performance of mitoxantrone prodrug nanoassemblies for cancer treatment.

Thermodynamic and structural properties of lipid-photosensitizer conjugates mixed with phospholipids: Impact on the formation and stability of nano-assemblies

The photosensitizer Phenalenone (PN) was grafted with one or two lipid (C18) chains to form pure nano-assemblies or mixed lipid vesicles suitable for photodynamic therapy. Mixtures of PN-C18 conjugates with stearoyl-oleoyl phosphatidylcholine (SOPC) form vesicles that disintegrate into bilayer sheets as the concentration of PN-C18 conjugates increases. We hypothesized that PN-C18 conjugates control the thermodynamic and structural properties of the mixtures and induce the disintegration of vesicles due to PN π-π-interactions.Monolayers were analyzed by surface pressure and grazing incidence X-ray diffraction (GIXD) measurements, and vesicles by differential scanning calorimetry and cryo-TEM. The results showed that PN-triazole-C18 (1A) and PN-NH-C18 (1B) segregate from the phospholipid domains. PN-(C18)2 (conjugate 2) develops favorable interactions with SOPC and distearoyl-phosphatidylcholine (DSPC). GIXD demonstrates the contribution of SOPC to the structuring of conjugate 2 and the role of the major component in controlling the structural properties of DSPC-conjugate 2 mixtures. Above 10 mol% conjugate 2 in SOPC vesicles, the coexistence of domains with different molecule packing leads to conjugate segregation, vesicle deformation, and the formation of small bilayer discs stabilized by the inter-bilayer π-π stacking of PN molecules.

Nucleic acids complexation with cationic elastin-like polypeptides: Stoichiometry and stability of nano-assemblies

Positively charged elastin-like polypeptides (ELPs) were synthesized for the compaction of genetic material. A recombinant ELP (VPGXG)40 with X = V,M (3:1) was post-modified in two steps to introduce chemoselectively either primary or secondary amine pendant groups at each methionine residue. Positively charged ELPs were characterized by SDS-PAGE, size exclusion chromatography, 1H NMR, potentiometric titrations and dynamic light scattering to assess their purity and determine their degree of functionalization, molecular weight, isoelectric point and thermo-responsive behaviour. Electrostatic complexation between the different ELP derivatives and nucleic acids was studied to determine the stoichiometry of ELPS/nucleic acids complex formation, and to find optimal conditions leading to stable nanoparticles with controlled size and surface potential. The stability of these complexes was investigated in the presence of salts at physiological concentrations and in the presence of surfactant. This study revealed that two regimes of stable nanoparticles in terms of size and charge can be obtained from the electrostatic complexation between the primary amine containing ELP derivative, ELP(-NH2), and plasmid DNA. Resulting complexes were found to be stable to dissociation for charge ratios up to 2.5 under physiological salt concentrations (154 mM NaCl), showing that plasmid DNA was completely condensed by the polycationic ELP and protected against electrolyte-mediated dissociation.

Interfacial behavior of PEGylated lipids and their effect on the stability of squalenoyl-drug nanoassemblies.

Squalenoyl-gemcitabine (Sq-Gem) and squalenoyl-dideoxycytidine (Sq-ddC) are amphiphilic prodrugs that self-assemble in water to form nanoassemblies (NAs) with well-defined structures and size. However, like other drug nanocarriers, these nanoassemblies are rapidly cleared from the blood stream by the reticulo-endothelial system. By adding squalenoyl-PEG (Sq-PEG) or cholesterol-PEG (Chol-PEG) to the squalenoyl prodrugs, composite nanoassemblies (CNAs) were formed, with different sizes and structures. The effect of the PEG-lipids on the formation and stability of these nanoassemblies was assessed by transmission electron microscopy, quasi-elastic light scattering and surface tension measurements in various conditions. The results revealed different stabilities with time for Sq-ddC and Sq-Gem nanoassemblies in aqueous medium, the latter being much less stable than the former. They also demonstrated that the presence of Sq-PEG or Chol-PEG in composite Sq-ddC nanoassemblies contributed to their rapid destabilization. The analysis of the adsorption kinetics of Sq-PEG into a prodrug monolayer below and above its critical aggregation concentration allowed getting a better insight into prodrug-lipopolymer molecular interactions, and their consequences on the formation of composite prodrug nanoassemblies.